Silent, readily-serviced electric fan construction



July 26, 1955 J, J, KUESER 2,713,970

SILENT, READILY-SERVICED ELECTRIC FAN CONSTRUCTION Filed June 30, 1952 United States Patient SILENT, READILY-SERVICED ELECTRIC FAN CONSTRUCTION John J. Kueser, St. Louis, Mo., assignor to Knapp-Monarch Company, St. Louis, Mo., a corporation of Delaware Application June 30, 1952, Serial No. 296,338

1 Claim. (Cl. 230-259) My invention relates to an improved silent fan construction characterized by case of assembly and disassembly and by simplicity of construction.

In the application of electric fans to domestic use, it is of great importance to minimize noises associated with operation of the induction motors used for this purpose. This is particularly true in the case of room heaters and coolers wherein large panels of metal form sounding boards which amplify and reinforce the sounds of the fan to increase the disturbance to the user.

While it has long been known that these fan noises can be overcome by the use of an elastic grommet sandwiched between the fan blade hub and the motor shaft, the use of such construction has entailed problems of assembly and disassembly and of anchoring the rubber to the shaft and to the fan blade hub. Gluing or other sealing arrangements between the surfaces of the grommet and the shaft and hub entail difficulties of manufacture and prevent disassembly of the apparatus for repairs. In the constructions heretofore available, the use of sim ple friction seats gives rise to intolerable slippage or at least to a construction wherein slippage can easily occur, with the consequent wear and ultimate failure.

The difiiculties of securing the elastic to the shaft and hub, on one hand, and slippage, on the other hand, are avoided by the construction of the present invention in which the shaft is knurled in a series of parallel grooves and protuberances along the axis of the shaft. It has been found that with this arrangement the tendency to slip at the inner periphery of the grommet, which is the place where such slippage is most likely to occur, is reduced to the point wherein the grip on the inner surface is essentially as tight as that on the outer surface. Since all fits are friction fits,'the unit may be readily assembled and disassembled without the use of special tools or breaking any surfaces joined by adhesive or otherwise.

In addition, the construction of the present invention retains the fan and grommet against longitudinal movement in relation to the shaft. Thus, while the unit can be easily assembled and disassembled, there is no tendency for the fan to creep either off the shaft or towards the motor.

It is therefore the object of the present invention to provide an improved fan construction in which noise is avoided by the use of an elastic grommet; in which the unit can be readily assembled and disassembled; and in which the tendency for radial slippage or longitudinal creep is eliminated.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the ap pended claim. My inventionitself, however, both as to its organization and method of operation, together with further objects and advantages thereof, will be best understood by reference to the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a side elevational view of a fan constructed 7 ures 2 and 3.

2,713,970 Patented July 26, 1955 in accordance with the present invention with parts broken away to show the motor construction;

Figure 2 is a view of the motor rotor and shaft assembly, the elastic grommet, and the fan blade and hub unit of the apparatus of Figure 1, all shown in exploded relation, and with parts shown in axial cross-section; and

Figure 3 is a greatly enlarged axial cross-sectional view of the shaft, grommet, and fan blade hub of the apparatus of Figures 1 and 2, all shown in axial crosssection.

As shown in Figure 1, the apparatus consists of a motor M having a protruding shaft 10 and a fan 36 located on the free end of the shaft. Typically the motor M is of the single phase induction type with a laminated core 14 with inner peripheral slots in which the winding 16 is disposed. The core is held in the stator frame 13 which at its end portions 20 and 22 receives ball bearings which support the shaft 10, one of these bearings being indicated at 24.

The motor rotor, indicated at 26, is typically and preferably of the squirrel cage type formed by magnetic laminations sandwiched together and having a series of peripheral slots. Copper or aluminum bars are disposed in the slots and have their ends joined together by conducting end rings 28 to form a continuous current conducting cage. The laminations of the rotor are secured to the shaft 10 by a tight friction seat.

Motors of the above type are characterized by the production of sound and vibration associated with the magnetic action in the motor. It is this noise, which takes the form of an A.-C. hum, that is most annoying to the user of the fan.

In accordance with the present invention the shaft 10 is knurled at its outboard or free end as shown in Fig- This knurling is in the form of a series of alternating grooves and protuberances in the surface of the shaft, as is shown at 30, the grooves being indicated at 30a, Figure 3, and the protuberances at 3%, Figure 3. This knurling is accomplished by rolling the shaft 10, under pressure, against a toothed knurling wheel, an operation that indents or grooves the surface of the shaft at the points of the teeth and forces the metal outwardly between the teeth of the knurling wheel to form the protuberances 30a.

A flanged elastic grommet 32 is received snugly over the knurled part of the shaft 10 as shown in Figure 3. This grommet in turn receives the inner sleeve or hub part 34 of the fan blade generally indicated at 36. The fan blade 36 has a blade part 38 which is preferably of stamped sheet metal which is fitted snugly over the reduced end portion 34a of the hub and the hub peened over at 3412 to secure the blade in place.

The grommet 32 is of rubber or other elastic material. It is of such size that, when it is in place as shown in Figure 3, the inner face of the grommet presses against the shaft 10 and the outer face of the grommet presses against the bore in the hub 34. In other words, a friction grip is established between the shaft and the grommet and between the grommet and the hub 34 of the fan blade 36.

In an embodiment of the present invention, the following approximate dimensions have been successfully employed:

71 inner diameter outer diameter A3" hub diameter inner diameter /2 long 3. Grommet 32 (when relaxed) 4. Hub s4 In practice applicant prefers to make the knurlings 30 of depth and height to cause the friction grip about the shaft 10 to be essentially the same as the grip between the hub 34 and the grommet. With this construction it is largely a matter of chance whether the slippage occurs at the shaft or at the hub when the fan 36 is forcefully turned in relation to the shaft 10. By this construction applicant has found that the tendency towards slippage is effectively overcome and at the same time the ready assembly and disassembly of the unit is preserved.

The protuberances 36a formed by the knurlings act to anchor the grommet 32 and blade 36 longitudinally as well as rotationally with reference to the shaft 10. This is highly important for it renders unnecessary any anchorage between the shaft and grommet to prevent creep toward or away from the free end of the shaft It). This effect is achieved when the grommet is of length and is so positioned as to extend outboard of the knurled portion 30 of the shaft.

While I have shown a specific embodiment of the present invention it will, of course, be understood that many modifications and alternative constructions can be made without departing from the true spirit and scope thereof. 1 therefore intend by the appended claim to cover all such modifications and alternative constructions as fall within the true spirit and scope of the claim.

What I claim as new and desire to secure by Letters Patent of the United States is:

A silent, readily-serviced fan construction comprising in combination; a motor having a frame, a shaft, and a rotor mounted on the shaft, the shaft having a knurled portion of limited extent outboard the frame, said knurled portion providing a multiplicity of axially-elongated protuberances extending in height outside the confines of the shaft and a corresponding multiplicity of alternate indentations extending in depth into the shaft, the depth of said indentations being substantially equal to the height of said protuberances; a fan blade having a cylindrical hub of size to fit over the shaft with an annular clearance space; and an elastic grommet sandwiched between the shaft and the hub in a compressed condition and extending outboard each side of said knurled portion of the shaft, the frictional engagement between the grommet and the hub being substantially equal to the frictional engagement between the grommet and the shaft.

References Cited in the file of this patent UNlTE-D STATES PATENTS 2,047,976 Lord July 21, 1936 2,097,318 Dowell Oct. 26, 1937 2,235,605 Bugatti Mar. 18, 1941 2,558,589 Skolfield June 26, 1951 

